The present invention is generally directed to fuel cell systems and more specifically to systems containing a dual function heat exchanger.
Solid oxide fuel (SOFC) systems operate at high temperatures in excess of 700° C. Frequently, heat transfer heat exchangers are provided to transfer by-product heat from the operating SOFC system to the heating systems of the facility in which the system is located.
During start-up of a SOFC system which utilizes steam reformation of a hydrocarbon fuel, water must be vaporized for the steam reforming process. This requires a device for accomplishing this purpose. In the prior art systems, dedicated humidification heat exchangers are frequently provided which use process heat in order to vaporize liquid water. However, these humidification heat exchangers often remain unutilized during steady-state operation of the system, especially if the inlet fuel stream is humidified by recycling a water vapor containing anode exhaust stream (i.e., the fuel exhaust stream) from the fuel cell stack into the fuel inlet stream being provided into the stack.